Date:	Wed, 30 Apr 2014 08:56:55 +0200
From:	Markus Pargmann <mpa@...gutronix.de>
To:	Xiubo Li <Li.Xiubo@...escale.com>
Cc:	mark.rutland@....com, broonie@...nel.org,
	gregkh@...uxfoundation.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 2/2] regmap: add DT endianness binding support.

Hi,

On Wed, Apr 30, 2014 at 12:43:49PM +0800, Xiubo Li wrote:
[...]
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index 8e8cea1..946e901 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -15,6 +15,7 @@
>  #include <linux/export.h>
>  #include <linux/mutex.h>
>  #include <linux/err.h>
> +#include <linux/of.h>
>  #include <linux/rbtree.h>
>  #include <linux/sched.h>
>  
> @@ -422,6 +423,132 @@ static void regmap_range_exit(struct regmap *map)
>  	kfree(map->selector_work_buf);
>  }
>  
> +enum regmap_endian_type {
> +	REGMAP_ENDIAN_REG,
> +	REGMAP_ENDIAN_VAL,
> +};
> +
> +/**
> + * of_regmap_endian_by_type() - Parse and lookup the endian referenced
> + * by a device node
> + * @np: pointer to clock consumer node

This is not the clock consumer, right?

> + * @type: type of consumer's endian input
> + *
> + * This function parses the device endian property, and uses them to
> + * determine the endian of the registers and values.
> + */
> +static int of_regmap_endian_by_type(struct device_node *np,
> +					enum regmap_endian_type type,
> +					enum regmap_endian *endian)
> +{
> +	if (!endian)
> +		return -EINVAL;
> +
> +	switch (type) {
> +	case REGMAP_ENDIAN_REG:
> +		if (of_property_read_bool(np, "big-endian-reg"))
> +			*endian = REGMAP_ENDIAN_BIG;
> +		else if (of_property_read_bool(np, "little-endian-reg"))
> +			*endian = REGMAP_ENDIAN_LITTLE;
> +		else
> +			*endian = REGMAP_ENDIAN_NATIVE;

You could also return an error code here as there was no DT property
found. This doesn't change to much in the code, just an idea.

Regards,

Markus

> +		break;
> +	case REGMAP_ENDIAN_VAL:
> +		if (of_property_read_bool(np, "big-endian-val"))
> +			*endian = REGMAP_ENDIAN_BIG;
> +		else if (of_property_read_bool(np, "little-endian-val"))
> +			*endian = REGMAP_ENDIAN_LITTLE;
> +		else
> +			*endian = REGMAP_ENDIAN_NATIVE;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int of_regmap_get_endian(struct device *dev,
> +				const struct regmap_bus *bus,
> +				const struct regmap_config *config,
> +				enum regmap_endian_type type,
> +				enum regmap_endian *endian)
> +{
> +	int ret;
> +
> +	if (!endian || !config)
> +		return -EINVAL;
> +
> +	/*
> +	 * Firstly, try to parse the endian from driver's config,
> +	 * this is to be compatible with the none DT or the old drivers.
> +	 * From the driver's config the endian value maybe:
> +	 *   REGMAP_ENDIAN_BIG,
> +	 *   REGMAP_ENDIAN_LITTLE,
> +	 *   REGMAP_ENDIAN_NATIVE,
> +	 *   REGMAP_ENDIAN_DEFAULT.
> +	 */
> +	switch (type) {
> +	case REGMAP_ENDIAN_REG:
> +		*endian = config->reg_format_endian;
> +		break;
> +	case REGMAP_ENDIAN_VAL:
> +		*endian = config->val_format_endian;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * If the endian parsing from driver's config is REGMAP_ENDIAN_DEFAULT,
> +	 * that means maybe we are using the DT node to specify the endianness.
> +	 */
> +	if (*endian != REGMAP_ENDIAN_DEFAULT)
> +		return 0;
> +
> +	/*
> +	 * Secondly, try to parse the endian from DT node if the
> +	 * driver config does not specify it.
> +	 * From the DT node the endian value maybe:
> +	 *   REGMAP_ENDIAN_BIG,
> +	 *   REGMAP_ENDIAN_LITTLE,
> +	 *   REGMAP_ENDIAN_NATIVE,
> +	 */
> +	if (dev) {
> +		ret = of_regmap_endian_by_type(dev->of_node, type, endian);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	/*
> +	 * If the endian parsing from DT node is REGMAP_ENDIAN_NATIVE, that
> +	 * maybe means the DT does not care the endianness or it should use
> +	 * the regmap bus's default endianness, then we should try to check
> +	 * whether the regmap bus has specified the default endianess.
> +	 */
> +	if (*endian != REGMAP_ENDIAN_NATIVE)
> +		return 0;
> +
> +	/*
> +	 * Finally, try to parse the endian from regmap bus config
> +	 * if in device's DT node the endian property is absent.
> +	 */
> +	switch (type) {
> +	case REGMAP_ENDIAN_REG:
> +		if (bus && bus->reg_format_endian_default)
> +			*endian = bus->reg_format_endian_default;
> +		break;
> +	case REGMAP_ENDIAN_VAL:
> +		if (bus && bus->val_format_endian_default)
> +			*endian = bus->val_format_endian_default;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * regmap_init(): Initialise register map
>   *
> @@ -518,17 +645,15 @@ struct regmap *regmap_init(struct device *dev,
>  		map->reg_read  = _regmap_bus_read;
>  	}
>  
> -	reg_endian = config->reg_format_endian;
> -	if (reg_endian == REGMAP_ENDIAN_DEFAULT)
> -		reg_endian = bus->reg_format_endian_default;
> -	if (reg_endian == REGMAP_ENDIAN_DEFAULT)
> -		reg_endian = REGMAP_ENDIAN_BIG;
> -
> -	val_endian = config->val_format_endian;
> -	if (val_endian == REGMAP_ENDIAN_DEFAULT)
> -		val_endian = bus->val_format_endian_default;
> -	if (val_endian == REGMAP_ENDIAN_DEFAULT)
> -		val_endian = REGMAP_ENDIAN_BIG;
> +	ret = of_regmap_get_endian(dev, bus, config, REGMAP_ENDIAN_REG,
> +				   &reg_endian);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	ret = of_regmap_get_endian(dev, bus, config, REGMAP_ENDIAN_VAL,
> +				   &val_endian);
> +	if (ret)
> +		return ERR_PTR(ret);
>  
>  	switch (config->reg_bits + map->reg_shift) {
>  	case 2:
> -- 
> 1.8.4
> 
> 

-- 
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